If I'm not mistaken those are interference patterns, created by the high and lows of the different waves, the variety of shapes are produced because the different wavelengths interfere with each other at different points.

(15-06-2013 02:58 AM)nach_in Wrote: If I'm not mistaken those are interference patterns, created by the high and lows of the different waves, the variety of shapes are produced because the different wavelengths interfere with each other at different points.

Yes, and it is dependent on the material and composition of the plate.

The standing waves will be different for different densities and thicknesses of the material.

Skepticism is not a position; it is an approach to claims.
Science is not a subject, but a method.

The salt crystals will be pushed away from wherever the material is beating up and down. They'll collect where the material is still. If you pump energy into the material at just the right speeds you'll get standing waves where some parts of the material are always still and others are moving. The salt will settle where it is still, and what you see are the shapes of these still portions of the material. They form part of the shape the sound wave.

You can create the same kinds of standing wave with a skipping rope or a slinky by holding one end still and beating the other end up and down at just the right frequency. Humans are actually surprisingly good at finding and matching these frequencies so it should come pretty naturally. The first "harmonic" is where the two ends are essentially still and the middle of the rope beats up and down. The second harmonic is found by beating the rope at twice the speed and will create an additional still point. You'll have the end, a wiggle, a still point, another wiggle, and the other end. Beating three times as fast creates three wiggles, etc. The material here is more complex so the patterns are more complex. The patterns themselves come about because energy is bouncing backwards and forwards in the system in such a way that it meets itself perfectly. It takes the same amount of time to travel from one end to the other as it does for the next beat to start, so the energy keeps building up at the same points so long as the frequency stays the same.

This works in the other direction, too. Send enough random noise into a material and it will start to beat at its natural frequency. All sound we hear is pretty much the product of a harmonic like this. Random noise is thrown into a string or a chamber and the noise that keeps coming back at the period the material is tuned to. What we hear back is the frequencies that have built up on themselves because they matched the natural frequencies of the material, while the other sounds fail to reflect in upon themselves and aren't heard.

Give me your argument in the form of a published paper, and then we can start to talk.

(15-06-2013 02:58 AM)nach_in Wrote: If I'm not mistaken those are interference patterns, created by the high and lows of the different waves, the variety of shapes are produced because the different wavelengths interfere with each other at different points.

(15-06-2013 05:31 AM)Chas Wrote: Yes, and it is dependent on the material and composition of the plate.

The standing waves will be different for different densities and thicknesses of the material.

(15-06-2013 05:41 AM)Hafnof Wrote: The salt crystals will be pushed away from wherever the material is beating up and down. They'll collect where the material is still. If you pump energy into the material at just the right speeds you'll get standing waves where some parts of the material are always still and others are moving. The salt will settle where it is still, and what you see are the shapes of these still portions of the material. They form part of the shape the sound wave.